1. Field of the Invention
The present invention relates to controlling liquid discharged from a blood parameter measurement cassette or other device during venting of the device while calibrating it by passing calibration gas through the device, and more generally to controlling incidental liquid discharged during a venting process of fluid-handling medical devices.
2. Description of the Related Art
Medical devices are often used during certain surgical procedures when various characteristics or parameters of blood are monitored in real time. For example, during open heart surgery the surgeon and other members of the surgical team often monitor the pH of the patient's blood as well as the concentration of certain blood gases such as carbon dioxide and oxygen. Measurement of blood parameters is often accomplished using optical sensors installed in a cassette connected to an extracorporeal blood circuit in fluid communication with the vascular system of the patient.
For best results, the optical sensors of blood parameter measurement systems require calibration before use. One calibration technique, described in U.S. Pat. No. 5,997,818 to Hacker which is incorporated herein by reference in its entirety, involves bubbling calibration gases through a sterile liquid in the cassette chamber to calibrate the optical sensors to a blood parameter monitoring device. The calibration gas is vented to atmosphere after bubbling through the liquid. An incidental vestige of liquid may expel from the chamber along with the calibration gas as it is vented from the chamber to the atmosphere.
Expelled liquid is undesirable since it may migrate into sensitive areas of the blood parameter monitoring device components and potentially cause negative effects to the electronic or optical equipment. However, the current state of the art allows incidental amounts of liquid to be expelled and potentially affect the monitoring and calibration equipment used in conjunction with the cassettes.
From a broader perspective, many medical devices that receive a liquid flow require a venting process before the device is used in a medical procedure to remove air or other gases that may be contained within the interior of the device. If the gas is not removed prior to use, the safety and/or efficacy of the medical procedure may be negatively affected. For example, gas bubbles inside a medical device may collect in the area of highest elevation within the device and impede the liquid flow thereby reducing the performance of the device. In addition, the gas could be inadvertently injected into a patient, resulting in known health risks.
Generally, whenever medical devices require a venting process to remove internal gases from a liquid, some potential exists for an incidental amount of the liquid to discharge from the device along with the gas. Discharged liquid related to venting can be problematic in the medical setting because of issues such as blood borne pathogens, cross-contamination of substances, slip and fall injuries, damage to sensitive equipment, and other safety concerns. A means for controlling the liquid discharged caused by a venting process would be beneficial to patients and practitioners in the medical setting.